1. Field of the Invention
The present invention relates to a pressurized medium for an inflator suitable for an inflator which is mounted in various kinds of vehicles to protect a passenger when a vehicle has received an impact from the lateral direction of the vehicle, an inflator and an air bag apparatus.
2. Description of Related Art
As an inflator for inflating type safety system of an automobile, in order to optimally protect a passenger in accordance with a position of a seat in a vehicle such as a driver side, a front passenger side next to the driver and the like, there are known various kinds of inflators such as an air bag inflator for a driver side, an air bag inflator for a front passenger side next to the driver, an air bag inflator for a side collision, an inflator for a curtain air bag, an inflator for a knee-bolster air bag, an inflator for an inflatable seat belt, an inflator for a tubular system and an inflator for pretensioner and the like.
Among these inflators, an inflator for a curtain air bag inflates and develops the air bag instantaneously to make a curtain having a thickness of some centimeters over windows of a vehicle when the vehicle has received an impact from a side of the vehicle. The curtain air bag is for the sake of protecting a passenger from an impact applied from the lateral direction of the vehicle, and from an impact when the vehicle is overturned. Therefore, it is necessary to shorten the period to the time when the air bag inflates as compared with a case in which the vehicle receives an impact from the front or from the behind. Further, on account of the period of overturning, the duration of the inflation has to be set to a few seconds.
As described above, in the inflator for a curtain air bag, the period to the time when the air bag inflates has to be shortened and the duration of the inflation has to be prolonged. Therefore, a method of inflating an air bag only with a pressurized medium, not with a gas generating agent is adopted. When a combustion gas of the gas generating agent is used, the air bag can be inflated instantaneously, however, because of a high temperature inside the inflated air bag, the combustion gas discharged into the air bag is cooled by a temperature difference with respect to the ambient temperature and the air bag is immediately deflated.
Meanwhile, when only the pressurized medium is used, since a temperature of the pressurized medium is lowered due to release of the pressure, the temperature in the air bag is also lowered. Therefore, the air bag is heated by a temperature difference with respect to the ambient temperature, and the duration of the inflation can be held for a few seconds. In view of securing safety of a passenger, however, it is required to maintain a higher internal pressure in the air bag for a longer period. Further, since the air bas is manufactured by sawing cloths, the pressured medium leaking from a seam thus reducing air bag internal pressure is also a factor of lowering of the air bag internal pressure and shortening of the inflating period of the air bag. Therefore, improvement based on this point will be an effective method.
Incidentally, as related conventional techniques, a device for inflating a flexible container using helium and hydrogen is disclosed in U.S. Pat. No. 5,527,066. A gas flow device for an air bag using a pressurized inert gas is disclosed in U.S. Pat. No. 5,782,486. An air bag apparatus for inflating an air bag by nitrogen or helium is disclosed in U.S. Pat. No. 3,680,886.